Tread.



H. P. MACDONALD.

TREAD.

APPLICATION FILED NO".

Patented May 26, 1914:.

WITNESSES:

wearing properties and thereby insures an extended life to the tread asa whole. Other advantages will occur to those familiar with the art.

Another advantage of the construction resides in the fact that, shouldthe tread wear unevenly for some reason or other, or become roughorjagged, it may be reversed, in which event the lower surface will in avery short time become as effective an abradant non-slipping surface asthe upper surface. It will be apparent that this will result inprolonging the life of the tread.

Another advantage incident to the construction is that in manufacturing,uniformity of product is secured'by reason of the fact that the abrasiveelements will always be in proper relation to the upper surfaceof thematrix, in view of the fact that the individual lumps are greater intheir least dimension than the thickness of the matrix, so that aportion will always project slightly above said surface. This alsosimplifies V manufacture.

metal plate having embedded therein a plurality of lumps of abrasiveeach of approxiof the tread and presenting substantially the sameaggregate surface of abrasive on each side of the tread so that thetension produced bythe casting on the two surfaces of the plate shall besubstantially equal so as to avoid warping.

2. As an article of manufacture, a tread member comprising asubstantially flat cast metal plate having embedded therein a pluralityof lumps of abrasive spaced substantially equi-distant from one anotherand each of approximately the same thickness as the body of the tread,the said lumps lying at least'flush with one face of the tread andpresenting substantially the same aggregate surface of abrasive on eachside of the plate so that the tension produced by the casting on the twosurfaces of theplate shall be SO nearly equal as to avoid warping.

In testimony whereof I have hereunto signed my name in the presence ofthe two subscribed witnesses.

HARRY P. MACDONALD.

Witnesses J. F. ARNOLD, C. C. GREENLEE, Jr.

